Maize growth and grain yield responses to a micronized humic product across soil types and annual weather patterns in Central Iowa, United States

Authors: Olk, Daniel - Dan; Dinnes, Dana; SCORESBY, RENE - Minerals Technologies (MTI); DARLINGTON, GERALD - Minerals Technologies (MTI); HURBURGH, CHARLES - Iowa State University; RIPPKE, GLENN - Iowa State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2021
Publication Date: 5/12/2021
Citation: Olk, D.C., Dinnes, D.L., Scoresby, R.J., Darlington, G.W., Hurburgh, C.R., Rippke, G.R. 2021. Maize growth and grain yield responses to a micronized humic product across soil types and annual weather patterns in Central Iowa, United States. Frontiers in Plant Science. 12. Article 672078. https://doi.org/10.3389/fpls.2021.672078.
DOI: https://doi.org/10.3389/fpls.2021.672078

Interpretive Summary: Application of humic products to field crops is claimed to increase crop yields, but supporting evidence is scarce for field studies, especially in the Corn Belt. In this study we evaluated the capability of one humic product to increase corn growth in four growing seasons and in both drier eroded hilltop soils and also in wetter soils at the bases of the hills for two production fields in Central Iowa. Annual weather patterns ranged across the four years from severe drought to nearly ideal distribution of rainfall. We found that humic product application noticeably increased corn grain yield in the drier years and on the hilltop soils, while no substantial benefit was observed in the wetter years and the lowland soils. The yield increase resulted primarily from longer ear length, not from increased availability of soil nutrients. These results identify the settings in Iowa corn production that will be most conducive to use of humic products. They also provide one explanation for inconsistent reports elsewhere on field effectiveness of humic products. These results will be informative for manufacturers and users of humic products in seeking optimal use of humic products. The results will also be of value to researchers of humic products.

Technical Abstract: Few field evaluations of humic products have been published for the U.S. Corn Belt, and very few studies globally have examined changes in humic product efficacy by environmental factors. Here we determined the effect of a micronized humic product on corn (Zea mays L.) growth and grain yield in two rainfed production fields in Central Iowa. The experimental design compared two application rates of the product to an unamended control. It was imposed in the corn phase of a corn-soybean (Glycine Max (L.) Merr.) rotation in 2012, 2014, and 2016 in one farmer’s production field and in a second field of the same farmer in 2013. Grain yield data acquired by mechanized combine were recorded for each of the two or three soil types found in each field. Maize grain yield increased significantly (P<0.10) with humic product application in two dry growing seasons on an eroded hilltop (“upland”) soil. Increases were 11% and 19% above the control for the two application rates in the droughtiest 2012 season, and 7% above the control for the higher application rate in the somewhat dry 2013 season. On a fertile, high-yielding sideslope soil, though, only a faint positive response occurred in one year. On a clayey, toeslope (“lowland”) soil the sole significant response was in 2012 with a significant increase of 14% above the control for one application rate and a numeric but nonsignificant increase by 6% for the other treatment. The yield boost was mostly due to increased ear length, especially of the shorter ears. Combine grain yields, grain weights of yield component samples, and leaf areas all demonstrated slight numeric increases for humic product treatments above the control in the vast majority of comparisons across years and soil types, with slightly better distinction in the upland transect. Yet statistical significance was reached only in the droughtier settings. The humic product had no broad effects on nutrient concentrations of the grain, stover, or young leaves or on several parameters of grain quality, although positive significant responses occurred in droughtier conditions for B and starch concentrations, while negative responses occurred in the lowland transect during the moist 2014 season. No effects of the humic product were observed on 13 soil properties. Application of this humic product improved corn growth in rainfed conditions in a high-yielding region and its efficacy varied predictably with environmental conditions, providing one potential explanation for inconsistent reports elsewhere of crop responses to humic products.